, Volume 85, Issue 3, pp 332–342

Ecological correlates of seed mass variation in Phoradendron juniperinum, a xylem-tapping mistletoe

  • Todd E. Dawson
  • James R. Ehleringer
Original Papers


We investigated several ecological correlates of seed mass variation in the hemiparasitic, xylemtapping mistletoe, Phoradendron juniperinum. Mean seed mass varied two-fold among plants between the ages of 4 and 14 years old and was positively correlated with parental plant age. Both the standard deviation and the coefficient of variation in mean seed mass decreased with increasing plant age demonstrating that, on average, younger plants produced seed with more variable mass. Nitrogen concentrations (mg nitrogen per gram of seed) of both the seed and “fruit” (pericarp) were not correlated with mass or the age of the parent plant from which the seed was taken. However, the nitrogen content per seed (mg nitrogen per seed) was positively correlated with the mean seed dry mass and the age of the seed parent, suggesting that the carbon to nitrogen ratio of individual seeds remained relatively constant as seed mass increased and plants grew older. Seed germination ranged between 20% and 86% and was positively correlated with mass and parental plant age. Heavier seeds (seeds from older plants) also had the highest root radicle growth rates. Furthermore, the final root radicle length after 76 d of growth was positively correlated with seed dry mass. When grown on a medium containing an extract prepared from the host plant foliage, all seeds showed lower germination, grew more slowly and had shorter overall root radicles, but had significantly greater development of the haustorial “disks” (the holdfast which forms the host-parasite junction in Phoradendron) than seeds grown on a control medium. Our results suggest that, on average, seeds of greater mass produced by older plants have a greater total resource pool per propagule (fruit + seed). This resource pool may be important in conferring a greater potential for dispersal (fruit), survival, colonization, and establishment.

Key words

Mistletoe Seed mass variation Establishment Carbon to nitrogen ratio Phoradendron juniperinum 


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  1. Atsatt PR (1979) On the evolution of leaf resemblance between mistletoes and their hosts. In: Musselman LJ, Worsham AD, Eplee RE (eds) Proceedings of the 2nd symposium on parasitic weeds. NC State University, RaleighGoogle Scholar
  2. Atsatt PR (1983) Host-parasite interactions in higher plants. In: Lange OL, Nobel PS, Osmond CB, Ziegler H (eds), 519–535. Encyclopedia of Plant Physiology, Physiological Plant Ecology III, Responses to the Chemical and Biological Environment, Vol 12C, Springer-Berlin, Heidelberg, New YorkGoogle Scholar
  3. Atsatt PR, Strong DR (1970) The population biology of annual grassland hemiparasites. I. The host environment. Evolution 24:278–291Google Scholar
  4. Baker HG (1972) Seed mass in relation to environmental conditions in California. Ecology 53:997–1010Google Scholar
  5. Baldwin JT, Speese BM (1957) Phoradendron flavescens: chromosomes, seedlings, and hosts. Am J Bot 44:136–140Google Scholar
  6. Beckman KM, Poth LF (1968) The influence of temperature on longevity and germination of seed of western dwarf mistletoe. Phytopath 58:147–150Google Scholar
  7. Begon M, Parker GA (1986) Should egg size and clutch size decrease with age? Oikos 47:293–302Google Scholar
  8. Bewley DJ, Black M (1985) Seeds: physiology of development and germination. Plenum, New YorkGoogle Scholar
  9. Black JN (1958) Competition between plants of different initial seed size in swards of subterranean clover (Trifolium subterraneum L.) with particular reference to leaf area and light microclimate. Aust J Agric Pes 9:299–312Google Scholar
  10. Calvin CL (1966) Anatomy of mistletoe (Phoradendron flavescens) seedlings grown in culture. Bot Gaz 127:171–183Google Scholar
  11. Cavers PB, Steel MG (1984) Patterns of change in seed weights over time on individual plants. Am Nat 124:324–335Google Scholar
  12. Choe HS, Chu C, Koch G, Gorham G, Mooney HA (1988) Seed weight and seed resources in relation to plant growth rate. Oecologia 76:158–159Google Scholar
  13. Clay K, Dement D, Rejmanek M (1985) Experimental evidence for host races in mistletoe (Phoradendron tomentosum). Am J Bot 72:1225–1231Google Scholar
  14. Cook CG, Wichard LP, Turner B, Wall ME, Egley GH (1966) Germination of witchweed (Striga lutea Lour): isolation and properties of a potent stimulant. Science 154:1189–1190Google Scholar
  15. Dawson TE, King EJ, Ehleringer JR (1990a) Age structure of Phoradendron juniperinum (Viscaceae), a xylem-tapping mistletoe: inferences from a non-destructive morphological index of age. Am J Bot 77:573–583Google Scholar
  16. Dawson TE, Ehleringer JR, Marshall JD (1990b) Sex-ratio and reproductive variation in the xylem-tapping mistletoe, Phoradendron juniperinum (Viscaceae). Am J Bot 77:584–589Google Scholar
  17. Epstein E (1972) Mineral Nutrition of Plants: principles and perspectives. John Wiley and Sons, Inc., New YorkGoogle Scholar
  18. Fenner M (1985) Seed Ecology. Chapman and Hall, LondonGoogle Scholar
  19. Galen C, Plowright RC, Thomson JD (1985) Floral biology and regulation of seed set and seed size in the lily, Clintonia borealis. Am J Bot 72:1544–1552Google Scholar
  20. Gill LS, Hawksworth FG (1961) The mistletoes—a literature review. USDA Tech Bull 1941, Washington D.C.Google Scholar
  21. Harper JL, Obeid M (1967) Influence of seed size and depth of sowing on the establishment and growth of varieties of fiber and oil seed flax. Crop Sci 7:527–532Google Scholar
  22. Harper JL, Lovell KG, Moore PH (1970) The shapes and sizes of seeds. Ann Rev Ecol Syst 1:327–356Google Scholar
  23. Johnson AW, Roseberry G, Parker C (1976) A novel approach to Striga and Orobanche control using synthetic germination stimulants. Weed Res 16:223–227Google Scholar
  24. Jones RJ, Quattar S, Crookston RK (1984) Thermal environment during endosperm cell division and grain filling in maize: effects of kernel growth and development in vitro. Crop Sci 24:133–137Google Scholar
  25. Kaplan RH, Cooper WS (1984) The evolution of developmental plasticity in reproductive characteristics: an application of the “adaptive coin flipping” principle. Am Nat 123:393–410Google Scholar
  26. Kaplan SL, Koller HR (1974) Variation among soybean cultivars in seed growth rate during the linear phase of seed growth. Crop Sci 14:613–614Google Scholar
  27. Kelley RO, Dekker RAF, Bluemink JG (1973) Ligand-mediated osmium binding: its application in coating biological specimens for scanning electron microscopy. J Ultrastruct Res 45:254–258Google Scholar
  28. Kennedy JR, Williams RW, Gray JP (1989) The use of Peldri II (a fluorocarbon solid at room temperature) as an alternative to critical point drying for biological tissues. J Electron Microsc Tech 11:117–125Google Scholar
  29. Kuijt J (1969) The biology of parasitic flowering plants. University of California Press, BerkeleyGoogle Scholar
  30. Kuijt J (1986) Observations on establishment and early shoot emergence of Viscum minimum (Viscaceae). Acta Bot Neer 35:449–456Google Scholar
  31. Lamont B (1983) Germination of mistletoes. In: Calder M, Bernhardt P (eds), 129–143. The biology of mistletoes. Academic Press, SydneyGoogle Scholar
  32. Marshall DL (1986) Effects of seed size on seedling success in three species of Sesbania (Fabaceae) Am J Bot 73:457–463Google Scholar
  33. May DS (1971) The role of populational differentiation in experimental infection of Prosopis by Phoradendron. Am J Bot 58:921–931Google Scholar
  34. Mazer SJ (1989) Ecological, taxonomic, and life history correlates of seed mass among Indiana dune angiosperms. Ecol Monogr 59:153–175Google Scholar
  35. McGinley MA (1989) The influence of a positive correlation between clutch size and offspring fitness on the optimal offspring size. Evol Ecol 3:150–156Google Scholar
  36. McGinley MA, Charnov EL (1988) Multiple resources and the optimal balance between size and number of offspring. Evol Ecol 2:77–84Google Scholar
  37. McGinley MA, Temme DH, Geber MA (1987) Parental investment in offspring in variable environments: theoretical and empirical considerations. Am Nat 130:370–398Google Scholar
  38. Meffe GK (1987) Embryo size variation in mosquito fish: optimality vs plasticity in propagule size. Copeia 1987(3):762–768Google Scholar
  39. Pate JS, Layzell DB (1981) Carbon and nitrogen partitioning in the whole plant; a thesis bases on empirical modeling. In: Bewley JD (ed), 94–134. Nitrogen and carbon metabolism. DW Junk, LondonGoogle Scholar
  40. Philippi T, Seger J (1989) Hedging one's evolutionary bets, revisited. Trends Ecol Evol 4:41–44Google Scholar
  41. Reading CJ (1986) Egg production in the common toad, Bufo bufo. J Zool 208:99–107Google Scholar
  42. Saghir AR (1979) Strigol analogues and their potential for Orobanche control. In: Musselman LJ, Worsham AD, Eplee RE (eds) Proceedings of the 2nd symposium on parasitic weeds. NC State University, RaleighGoogle Scholar
  43. Salisbury EJ (1974) Seed size and mass in relation to environment. Proc Roy Soc Lond, B, 186:83–88Google Scholar
  44. Sallé G (1983) Germination and establishment of Viscum album L. In: Calder M, Bernhardt P (ed), 145–159. The biology of mistletoes. Academic Press, SydneyGoogle Scholar
  45. Schaal BA (1980) Reproductive capacity and seed size in Lupinus texansis. Am J Bot 67:703–709Google Scholar
  46. Schulze E-D, Ehleringer JR (1984) The effect of nitrogen supply on growth and water use efficiency of xylem mistletoes. Planta 162:268–275Google Scholar
  47. Schimpf DJ (1977) Seed weight of Amaranthus retroflexus in relation to moisture and length of growing season. Ecology 58:450–453Google Scholar
  48. Semlitsch RD (1985) Reproductive strategy of a facultatively paedomorphic salamander Ambystoma talpoideum. Oecologia 65:305–313Google Scholar
  49. Sinnott EW (1921) The relationship between body size and organ size in plants. Am Nat 55:385–403Google Scholar
  50. Silvertown JW (1981) Seed size, lifespan and germination date as coadapted features of plants life history. Am Nat 118:860–864Google Scholar
  51. Smith CC, Fretwell SD (1974) The optimal balance between size and number of offspring. Am Nat 108:499–506Google Scholar
  52. Stanton ML (1984) Seed variation in wild radish: effect of seed size on components of seedling and adult fitness. Ecology 65:1105–1112Google Scholar
  53. Stanton ML, Bereczky JK, Hasbrouck HD (1987) Pollination thoroughness and maternal yield regulation in wild radish, Raphanus raphanistrum (Brassicaceae). Oecologia 74:68–76Google Scholar
  54. Stewart GR, Press MC (1990) The physiology and biochemistry of parasitic angiosperms. Ann Rev Plant Physiol Plant Mol Biol 41:127–151Google Scholar
  55. Thompson K, Rabinowitz D (1989) Do big plants have big seeds? Am Nat 133:722–728Google Scholar
  56. Thomson VE, Mahall BE (1983) Host specificity by a mistletoe, Phoradendron villosum (Nutt.) Nutt. subsp. villosum, on three oak species in California. Bot Gaz 144:124–131Google Scholar
  57. Tinnin RO, Calvin CL, Null RL (1971) Observations on the establishment of seedlings of Phoradendron californicum on Prosopis juliflora. Phytomorph 12:313–320Google Scholar
  58. Watson MA, Casper BB (1984) Morphogenetic constraints on patterns of carbon distribution in plants. Ann Rev Ecol Syst 15:233–258Google Scholar
  59. Weis IM (1982) The effects of propagule size on germination and seedling growth in Mirabilis hirsuta. Can J Bot 60:1868–1874Google Scholar
  60. Wolf LL, Hainsworth FP, Mercier T, Benjamin R (1986) Seed size variation and pollinator uncertainty in Ipomopsis aggregata (Polemoniaceae). J Ecol 74:361–371Google Scholar
  61. Wulff RD (1986) Seed size variation in Desmodium paniculatum. II. Effects on seedling growth and physiological performance. J Ecol 74:99–114Google Scholar
  62. Zimmerman JK, Weis IM (1983) Fruit size variation and its effect on germination and seedling growth in Xanthium strumarium. Can J Bot 61:2309–2315Google Scholar

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Todd E. Dawson
    • 1
  • James R. Ehleringer
    • 1
  1. 1.Department of BiologyUniversity of UtahSalt Lake CityUSA
  2. 2.Section of Ecology and SystematicsCornell UniversityIthacaUSA

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